Radar video output is conventionally displayed by a monochrome plan position indicator. With an automatic tracking system, target velocity can be digitally read out separately. An operator's response currently depends only on the brightness of the target returns. While plan position indicators have historically been monochrome, and in fact early models had no color capabilities, later plan position indicators had limited color capabilities but these were never widely used. In fact, some current plan position indicators are implemented using a raster display (i.e., the SPA-25G, a U.S. Navy raster PPI) which has the potential for good color.
In U.S. Pat. No. 3,882,502 (Peabody et al), a moving target indication display system is disclosed wherein the target display color indicates the speed of the target. The hue of the display target is a function of its speed, and the targets for each stored scan are repetitively displayed in rapid succession so that a moving target is displayed on a CRT as a series of flashing dots on a line of residual light.
In U.S. Pat. No. 3,878,422 (Brown et al), a gas discharge phosphor-containing display which identifies a moving body by color without computer processing is disclosed. This is made possible by utilizing a multiple gaseous discharge display panel so that a color produced by a phosphor and gas discharge at a cell indicates a moving body whose velocity is indicated by the decay time of the phosphor.
In U.S. Pat. No. 3,697,990 (Emch), the use of a plan position indicator display and the gathering and processing of target range and elevation information is disclosed. The elevation and range signals are placed in a hold circuit and are then scaled and displayed on separate devices.